A federal judge has ordered the U.S. Department of Housing and Urban Development to implement an Obama-era rule on Jan. 1 that would give low-income families greater access to housing in more affluent neighborhoods.

The 2016 rule was designed to break up areas of concentrated poverty in two dozen metro regions, from Atlanta and Charlotte to San Diego and Honolulu.

It would operate by taking into account the rental prices in specific neighborhoods — instead of averaging across an entire metropolitan area — making it easier for poor people to afford apartments in middle-class neighborhoods with better schools, lower crime rates and more job opportunities.

Under the current system, families receiving public rental assistance have been concentrated in deeply segregated, high-poverty communities.

A coalition of civil rights organizations sued the Trump administration in October after HUD Secretary Ben Carson announced that the agency would delay implementing the rule by nearly two years to allow the new administration time to fully understand its effects. Housing industry groups, including the National Association of Home Builders, lobbied against the rule, arguing that it would lead to disinvestment in inner city neighborhoods.

Chief Judge Beryl A. Howell, appointed to the U.S. District Court for the District of Columbia by President Barack Obama, ruled on Dec. 23that HUD’s decision to delay implementing the rule was “arbitrary and capricious.” She said the agency failed to show sufficient reason for a pause, and that a delay would irreparably harm the plaintiffs: a Hartford, Conn., mother of five and a Chicago mother trying to move their families to safer suburban communities.

“It’s long overdue that our federal government remedy the massive disparities in wealth and education its policies continue to produce, and modest rules like this one play an integral role in leveling the playing field for blacks, Latinos, and low-income Americans,” Sherrilyn Ifill, president and director-counsel of the NAACP Legal Defense and Educational Fund, said in a statement.

The NAACP Legal Defense and Educational Fund was among the half-dozen groups that challenged HUD’s efforts to delay the rule. “Suspending this rule was yet another attack by this administration on communities of color,” Ifill said. “By restoring the prior rule, this injunction is a key step toward expanding equal opportunity in all aspects of American life.”

A spokesman for HUD declined to comment this week on Howell’s decision. In an August blog post, the agency said it was trying to give local public housing agencies more time to prepare before it mandated the changes.

More than 200,000 families in two dozen communities will now have greater choices about where to live, said Philip Tegeler, president and executive director of the Poverty & Race Research Action Council, which was also part of the lawsuit.

“This represents a new opportunity for tens of thousands of families with housing vouchers,” Tegeler said. “It’s about the right to choose where to live and the right not to be segregated. Good housing policy does not confine families to high poverty neighborhoods.”

Families with incomes low enough to receive Section 8 vouchers have little say over where to live because it is generally left up to individual landlords whether to accept the housing vouchers. And those vouchers are often too low to cover rent in more affluent neighborhoods, relegating families to clusters of apartments in poor, highly segregated areas.

The new rule addressing that problem was issued in November 2016 by then-HUD Secretary Julián Castro after years of study and public debate.

Housing agencies in 23 metro areas will now be required to adopt “small area fair market rents,” which tie voucher subsidies to specific Zip codes. It would, in essence, redistribute the value of Section 8 rental vouchers, providing higher government subsidies for apartments in more expensive communities and lower subsidies for units in poor neighborhoods.

Such a rule was first rolled out in Dallas in 2010 as part of a fair housing settlement. Since then, pilot programs have been instituted in Chattanooga, Tenn.; Laredo, Tex.; Long Beach, Calif.; Cook County, Ill.; and Mamaroneck, N.Y.

Studies have shown that moving low-income families into wealthier communities results in better lives for their children, who are eventually more likely to attend college, earn more money, and reside in better neighborhoods as adults.